The effects of phorbol myristate acetate and Cytochalasin B are being investigated in the following areas: 1. Relationship of dose of PMA to cyclic GMP levels in 3T3 cells. 2. Cyclic GMP levels in lymphocytes. 3. Cyclic GMP levels in leukocytes. 4. CB and virus budding. 5. Relationship of cell number of cells involved in DNA synthesis to dose of PMA.